Endodontics or root canal therapy is that branch of dentistry that deals with the diseases of the dental pulp and periradicular tissues. One aspect of endodontics comprises the treatment of infected root canals by the removal of diseased pulp tissues, using biomechanical cleaning and shaping and subsequent filling of the pulp cavity (root canal). The access opening to the root canal must be sealed and the tooth restored. The objective in root canal therapy is to prevent leakage of toxic products from the coronal part of the tooth into the root canal system. The placement of a barrier material under the modified post assists in accomplishing this goal.
Root canal therapy is generally indicated for teeth having sound external structures but having diseased, dead, or dying pulp tissues. In such teeth, the pulp tissue and excised portions of the root should be replaced by a biocompatible substitute. The gold standard for filling the root canal is gutta percha and root canal sealer. Micro-leakage from the coronal portion of the tooth can pass through the gutta percha, filling to the apical portion to cause an abscess to form.
One technique for the preparation of a root canal involves creating a coronal straight line access opening with a conventional dental drill. The access opening in this technique is in the shape of a rhomboid inlay preparation, in the lingual surface of the anterior tooth. This facilitates the pattern withdrawal of the orifice seal and the connected modified post extension. In posterior teeth the access preparation is made through the occlusal tooth surface. A round bur is used for gross removal of pulp material from the pulp chamber through the coronal access opening. The canal orifices are located irrigated with sodium hypochlorite solution. The canals are negotiated with narrow files to establish the glide path of the canal. These files are rotated using a balanced force technique until free access to the foramen is reached. Apex locators are used to verify the length of the instrumented canal to the apex. Hand files are used to size #20, and then followed with nickel titanium rotary systems. Debris is removed from the root canal by flushing and evacuation after each instrument use. The root canals are cleansed of all diseased tissue and pulpal remnants. Following chemical antisepsis, the instrumented canal is ready for filling.
Current techniques typically fill the root canal with gutta percha, sealer, or resin. If posts are used, they are either active or passive, metal or fiber. A cosmetic and functional crown made of porcelain fused to metal is usually attached to the post and core. The placement of metal posts can result in perforations or fractures which may contribute to later tooth damage. Porcelain fused to metal crowns often show a dark unaesthetic hue at the cervical margin between the tooth and gingiva.